A catalytic cycle has been proposed for the acid-catalyzed hydrolysis of ethyl…

CHEMISTRY · Multi-part · A Level · Chemistry · Introduction to organic chemistry · Introduction to organic chemistry

Problem

A catalytic cycle has been proposed for the acid-catalyzed hydrolysis of ethyl acetate (

\mathrm{CH_3COOCH_2CH_3}

) in aqueous solution at 298 K. The elementary steps are numbered in the order in which they occur. Step 1

\mathrm{H_3O^+ \; + \; CH_3COOCH_2CH_3 \; \longrightarrow \; CH_3C(OH)OOCH_2CH_3 \; + \; H_2O}

Step 2

\mathrm{CH_3C(OH)OOCH_2CH_3 \; + \; H_2O \; \longrightarrow \; CH_3C(OH)OOH \; + \; CH_3CH_2OH}

Step 3

\mathrm{CH_3C(OH)OOH \; \longrightarrow \; CH_3COOH \; + \; H_3O^+}

Transient proton transfers within the reaction medium are implicit and need not be written. Assume no other reactions occur. (a) Show that the three elementary steps combine to yield the experimentally observed overall equation

\mathrm{CH_3COOCH_2CH_3 \; + \; H_2O \; \longrightarrow \; CH_3COOH \; + \; CH_3CH_2OH}

. (b) Construct a chronological list of all unique chemical species encountered in the mechanism. For each species, indicate at which step(s) it is produced and at which step(s) it is consumed. (c) Using your list from part (b), classify each species as reactant, product, intermediate, or catalyst. Justify every classification with explicit reference to the production–consumption information. (d) The rate-determining step is found experimentally to be Step 1. Discuss how this information, together with your classifications, supports the designation of

\mathrm{H_3O^+}

as a catalyst rather than an intermediate.

Related theory

Browse the problem library